While some public libraries around the country offer digital copies of books, the selections are generally rather limited. But a pair of new services is putting the entire card catalog at the fingertips of tablet and smartphone owners. Both Scribd and Oyster began offering e-book subscription services this month, giving avid readers access to a library of thousands of titles for a small monthly charge. (Scribd asks $9 per month, while Oyster charges $10.) Call it the Netflix-ization of the literary world.

While e-readers and tablets are becoming more prevalent, traditional books still make up the majority of people’s reading habits.

And sure, when you put it in that context, a monthly subscription fee for unlimited book rentals may seem like an obvious idea, but it’s a model that had to wait for technology to catch up. While e-readers and tablets are becoming more prevalent, traditional books still make up the majority of people’s reading habits.

That’s changing fast, though. A study by USA Today and the website Bookish found 40 percent of adults own an e-reader or a tablet — more than double the numbers from less than two years ago. And 35 percent of those with e-reading devices say they’re reading more.

“Since starting Scribd six years ago, we have … [gathered] data on what readers and publishers want,” said Trip Adler, CEO and co-founder of Scribd. “Those insights have helped us build a product that we believe delivers on a new and better reading experience.”

Oyster, like Scribd, has agreements with HarperCollins, but the start-up says it has also struck deals with Houghton Mifflin, Rodale and several independent publishers, giving it a catalog of 100,000 copyrighted books. Among its selections are books by Neil Gaiman, Dave Eggers and Kenneth C. Davis. But simply having a big catalog of reading material won’t be enough to succeed in what is becoming a crowded marketplace.

“We know that this product is much more than monthly books for a monthly price,” says Eric Stromberg, co-founder and CEO of Oyster. “Today people are looking for something much deeper, and they’re looking for relationships with their products. We’re excited about bringing that full experience — things like getting recommendations from friends or finding books from experts.”

Low-cost, all-you-can-eat subscriptions are popular with consumers, but some content creators complain that they’re losing money.

Early adoption rates for the service have been encouraging. While neither company will give specific subscription numbers, Scribd (which already had an established user base of 80 million users on its website) notes that within the first two weeks of its service, subscribers spent the equivalent of 9.6 years reading books — with one reader devoting 45 hours in a single week to reading. Oyster, which just emerged from a closed beta last week, says its readers hit the 1-million-page mark in 10 days. The second million took just six days — and the third million came in three.

To spur that growth, the company launched an iPad version of its app as it emerged from beta. (iPad is by far the most popular platform for Scribd users.) And while the company declined to address any specific future plans, it indicated an Android version is in the works as well.

Streaming services may be popular with consumers, thanks to their low-cost, all-you-can-eat model, but in the music world, at least, some content creators have complained that they’re losing money in the process. Cracker and Camper Van Beethoven singer-guitarist David Lowery earlier this year revealed that his song “Low” had been played 1,159,000 times on Pandora in three months — yet he had only been paid $16.89. That’s the sort of feedback that might scare away writers and cash-starved publishers.

Stromberg, though, says Oyster is attempting to be more fair to authors. “In terms of what the deals look like, I would say they do look very different,” he says. “We have put a lot of thought into this. To make this a sustainable business, we have to deliver value to publishers and authors.”

For every book read completely, the company says, a user browsed an average of 4.5 other books.

Adler says that the unlimited subscription model works in authors’ favor another way. It not only adds flexibility, it also reduces pressure for readers (who might not purchase or sample a book if it requires a financial investment every time), which exposes them to new writers. For every book read completely, the company says, a user browsed an average of 4.5 other books.

“In the world of print books, the standard transactional business model exists,” he said in an open letter to Scribd users. “As books have gone digital, the same business model has been preserved, where the consumer spends money and in exchange, gets a digital file … We believe removing the paywall at every step in the transactional model encourages readers to read more, including new readers that might not have previously purchased that book, essentially expanding the market for reading books digitally and growing revenue for publishers and authors.”